Lec09 - Lecture 9 Lecture 9-1 Capacitance Review d A •Suppose the capacitor shown here is charged to Q and then the battery disconnected •Now

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Unformatted text preview: Lecture 9 Lecture 9-1 Capacitance Review d A----- + + + + •Suppose the capacitor shown here is charged to Q and then the battery disconnected . •Now the plates are pulled apart so that the final separation is d 1 ( > d ) . •How do the quantities Q, U, C, V, E change? • By how much? 1 1 d U U d = C d d C 1 1 = V d d V 1 1 = Q: U: C : V : E: remains the same.. no way for charge to leave. increases.. add energy to system by separating decreases.. since d increases increases.. since C decreases, but Q remains same remains the same... depends only on charge density What if battery remains connected? Lecture 9 Lecture 9-2 Capacitors in Parallel Equivalent Capacitor: ≡ V is common 1 2 3 1 2 3 q q q V C C C ⇒ = = = q C V = where 1 2 3 q q q q = + + 2 3 1 1 2 3 eq q q q C C V C C = + + ∴ + + = Consistent with parallel- plate capacitor result of A C A d ε = ∝ Lecture 9 Lecture 9-3 Capacitors in Series ≡ Equivalent Capacitor: q C V = where 1 2 3 V V V V = + + 1 2 3 1 2 3 1 1 1 1 eq V V V q C C C C + + ∴ = = + + Consistent with parallel- plate capacitor result of 1 1 A C d d or d C ε = ∝ ∝ 11 22 33 qC V CV CV ⇒ = = = q is common Lecture 9 Lecture 9-4 Conductor inserted between plates •Two capacitors of area A in series- Q- Q a b •A parallel-plate capacitor with conductor inserted in the middle ≡ E=0 outside capacitors +q +q-q-q q E A ε = E=0 in conductor q E A ε = between plates between plates 1 1 1 a b a b ab C C C A A A ε ε ε + = + = + = A C ab ε ⇒ = + Lecture 9...
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This note was uploaded on 04/07/2008 for the course PHYS 241 taught by Professor Wei during the Spring '08 term at Purdue University-West Lafayette.

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Lec09 - Lecture 9 Lecture 9-1 Capacitance Review d A •Suppose the capacitor shown here is charged to Q and then the battery disconnected •Now

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